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November 20, 2023, 16:38 |
Restart overset simulation from latest time
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#1 |
Member
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Hi Foamers,
I am struggling with an overset simulation. I ran a simulation to the time XXX and stopped it there. In a second thought I wanted to restart it from there with a shorter interval of write time. Trying this always gives me the same problem. -> The mesh courant number is much too high and I do not know how to avoid this in the initial start from time XXX. In the second time step the velocity of the overset mesh is much too high which seems to be the result of the initial problem. After this mismatch the simulation does not get better.... I tried to set the time stepping to really very low numbers fot the initial calculation but this seems to be not related in the initial mesh courant number.... Anybody got experience how to fix this? Best regards, Michael |
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November 20, 2023, 17:00 |
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#2 |
Member
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Initial logfile from time XX, Courant 0.8 was the courant from running simulation at the first start. It ran well over a long time so this problem seems only related to the restart I think. First, initial step of the reastart:
Code:
Starting time loop Courant Number mean: 0.002566905784 max: 0.798598669498 deltaT = 1e-12 Time = 7 forces forces: rho: rhoInf Freestream density (rhoInf) set to 1.2 Not including porosity effects 6-DoF rigid body motion Centre of rotation: (4.52050459585e-27 9.36037226369e-28 3.48672357583e-26) Centre of mass: (4.52050459585e-27 9.36037226369e-28 3.48672357583e-26) Orientation: (1 1.89886146867e-25 3.56446691711e-23 -1.89886146867e-25 1 -1.4704682721e-23 -3.56446691711e-23 1.4704682721e-23 1) Linear velocity: (9.0410091917e-15 1.87207445274e-15 6.97344715165e-14) Angular velocity: (2.9409365442e-11 7.12893383421e-11 -3.79772293735e-13) DILUPBiCGStab: Solving for yPsi, Initial residual = 0.00454392990427, Final residual = 9.46945338613e-06, No Iterations 69 inverseDistance : detected 3 mesh regions zone:0 nCells:309288 voxels:(27 27 27) bb:(-0.40000045141 -0.397980507516 -0.500000747277) (-0.0399704184464 7.47279699828e-07 0.0200152408993) zone:1 nCells:2488 voxels:(27 27 27) bb:(-2.00000058403 -2.00000092056 -2.50000150997) (-1.19999788023 -1.1999981944 -1.49999849003) zone:2 nCells:21024 voxels:(27 27 27) bb:(-2.00000058403 -2.00000092056 -2.50000150997) (-1.19999788023 -1.1999981944 -1.49999849003) Overset analysis : nCells : 332800 calculated : 330360 interpolated : 1501 (from local:1055 mixed local/remote:446 remote:0) hole : 939 Mesh Courant Number mean: 0.0225261263018 max: 545.439207769 PIMPLE: iteration 1 ... Code:
Courant Number mean: 0.0484307886207 max: 201.289335348 deltaT = 3.97437846679e-15 Time = 7 forces forces: rho: rhoInf Freestream density (rhoInf) set to 1.2 Not including porosity effects 6-DoF rigid body motion Centre of rotation: (-2.3195495872e-11 1.08337649798e-11 -6.60471118518e-11) Centre of mass: (-2.3195495872e-11 1.08337649798e-11 -6.60471118518e-11) Orientation: (1 -8.81915728871e-14 -1.30487618269e-08 8.82711033301e-14 1 6.09486510264e-09 1.30487618269e-08 -6.09486510264e-09 1) Linear velocity: (-11672.5148678 5451.80338024 -33236.4481157) Angular velocity: (-3067078.36386 -6566441.48812 44.4000685119) DILUPBiCGStab: Solving for yPsi, Initial residual = 0.0135703272124, Final residual = 7.40960574936e-06, No Iterations 77 inverseDistance : detected 3 mesh regions zone:0 nCells:309288 voxels:(27 27 27) bb:(-0.40000045141 -0.397980507516 -0.500000747277) (-0.0399704184464 7.47279699828e-07 0.0200152408993) zone:1 nCells:2488 voxels:(27 27 27) bb:(-2.00000058403 -2.00000092056 -2.50000150997) (-1.19999788023 -1.1999981944 -1.49999849003) zone:2 nCells:21024 voxels:(27 27 27) bb:(-2.00000058403 -2.00000092056 -2.50000150997) (-1.19999788023 -1.1999981944 -1.49999849003) Overset analysis : nCells : 332800 calculated : 330543 interpolated : 1318 (from local:955 mixed local/remote:363 remote:0) hole : 939 Mesh Courant Number mean: 9.3848858359e-10 max: 2.21983969752e-05 PIMPLE: iteration 1 ... Any help is welcome. Last edited by Wowbagger; November 20, 2023 at 17:02. Reason: Kindness ;) |
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November 29, 2023, 09:37 |
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#3 |
New Member
Ranjodh Rai
Join Date: Feb 2021
Posts: 3
Rep Power: 5 |
Hi, I have this same problem and it's because the original dynamicMeshDict is read so centre of rotation etc. are set back to their original positions. Unfortunately I don't know a way around this; did you manage to find a solution?
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November 30, 2023, 07:19 |
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#4 |
Member
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Hi Ranj,
thanks for that hint! This sounds like the problem. If so, it is possible to change the position and motion of the body in the dynamicMeshDic, etc and restart with that. I will try this and give you feedback. Thanks a lot! Best regards, Michael |
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November 30, 2023, 13:47 |
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#5 |
Member
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I made this short test without success.
But I found out the important part I think: Reconstructing the latest time and have a look to it in paraView showed that the overset mesh did not move. Therefore I suggest that this position is always the reference for the calculation with the pointDisplacement folder. I tried different ways to get the latest simulated time step into reconstructed form but without success. Does anybody knew: --> Is there a way to reconstruct the latest time step in overset mesh? Maybe I missed the important bit... Any help welcome. Best regards Michael |
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December 1, 2023, 10:32 |
overset openfoam
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#6 | |
New Member
Diyanosh Hedayati
Join Date: Jul 2021
Location: Iran, Rasht
Posts: 3
Rep Power: 5 |
Quote:
I am a newbie to CFD, but recently I've been able to simulate a 3d floating object using overset mesh, although there are tons of issues which I still don't know. You have executed your model for 7 seconds, which is pretty good and indicates your model is working. But, suddenly, your solution diverges. you want to see what causes this problem and you want to reduce the write Interval to capture more details of divergence. right? I can't understand what's the point in reconstructing the latest time step? You can change the controlDict parameters, including write interval on the fly. Did you try to delete some (2 or 3) solved folders from processor* directories and then re-run the simulation? Since in the overset, the mesh doesn't deform, so running from the last time step won't be an issue. In the former case (deforming meshes as in mesh morphing), you need to do some considerations which are not necessary here. |
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December 2, 2023, 10:24 |
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#7 | ||
Member
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Quote:
Quote:
Code:
I can't understand what's the point in reconstructing the latest time step? Reconstructing the latest time shows differences in paraview: -looking to the decomposed case - everything is fine like the in the running aborted simulation. -looking into the reconstructed case - I see the overset mesh in the original position at start without any change. Therefore I think the restart is related to this. Code:
You can change the controlDict parameters, including write interval on the fly. Did you try to delete some (2 or 3) solved folders from processor* directories and then re-run the simulation? I tried to re-run in some time before - while I was working on the case to run. It did not work and I thought this was related to some bad numerics. Now the case is running fine but I can not re-start from latest time. And now I believe this is related to some overset stuff which I do not know so far or there is still a bug... Code:
Since in the overset, the mesh doesn't deform, so running from the last time step won't be an issue. In the former case (deforming meshes as in mesh morphing), you need to do some considerations which are not necessary here. But the position of the overset mesh are totally different from the very start to the latest time step... |
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December 4, 2023, 04:45 |
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#8 | |
New Member
Diyanosh Hedayati
Join Date: Jul 2021
Location: Iran, Rasht
Posts: 3
Rep Power: 5 |
Quote:
Thank you so much for your detailed response, So it seems the problem is related to existing overset bugs that should be solved in the next updates. First: May I ask you to share your case files?? Second: In my opinion, one of your last resources is to re-mesh everything again. These steps may be obvious for you, but to be used for others, try this procedure: 1) Reconstruct to your latest time step (your_last_time_step folder creates). 2) Make another folder resembling your case (background and overset). In the background directory, make an 'empty folder' named your_last_time_step. 3) Copy the "constant" and the "system" folders from the former "background" and "overset" directories to the new "background" and "overset" ones. 4) Modify the dictionaries, especially your write intervals and starting time, which should be the same as the last time step you reconstructed before. 5) In the "background directory", update the centre of mass in dynamicmeshDict according to your latest log file. 6) In the "overset directory", modify your blockmesh according to the updated centre of mass and the controlDict such as starting time. 7) If you have a 6dof body, it might be introduced by an STL file. You need to make an STL file from the latest position of your body. So: a) copy "points" from reconstructed/polymesh to background/constant/polymesh b) extract STL file from your patch using surfaceMeshTriangulate (in openfoam foundation versions this tool exists ), e.g. : surfaceMeshTriangulate -patches '(your patch or object)' new_stl_file.stl c) move the created STL file to the overset/constant/triSurface d) modify surfaceFeatureExtractDict and snappyHeshDict according to the new STL file. e) execute all commands related to mesh generation as before (blockMesh, snappy, mergeMesh , ...) f) execute mapFields to mirror field values from the reconstructed folder to the created your_last_time_step folder: mapFields ../former_backgrounf_directory -sourceTime your_last_time_step -mapMethod cellPointInterpolate -noFunctionObjects -consistent g) copy pointDisplacement file from 0 directory (former background directory) to the your_last_time_step folder (new background directory). h) copy "uniform" folder from reconstructed folder (former background directory) to the your_last_time_step (new background directory) 8) re-run the simulation. Best regards, Diyanosh |
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December 4, 2023, 16:58 |
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#9 |
Member
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Hi Diyanosh... ...are you sure you are a OpenFOAM newby?! ^^ Thanks a lot for your detailed description of the steps for the restart. I took in account that it is needed to get a new mesh but I was not aware about the practises in step 7. I will try it as soon as I got a few hours to work on that again. But I think it will be earliest next week. However I will give feedback. Regarding the question to my case files: You got PN. Best regards Michael |
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February 25, 2024, 16:06 |
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#10 |
Member
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Finally after a long time I did it.
With the help of Diyanosh I was able to restart at the given time. Most points where correct but I did not find a way to work with openfaom on point 7a & 7b. I updated Diyanoshs work therefore with my findings. Some steps are slightly different due to simple preference: 1. Reconstruct the latest time Step 2. Make a copy of the folders (background & overset) with foamCloneCase. 3. Copy the reconstructed latestTime from the old background folder into the new one. 4. Modify the dictionaries, especially your write intervals and starting time, which should be the same as the last time step you reconstructed before. 5. In the "background directory", update a) the centre of mass in dynamicmeshDict according to your latest log file. b) same with velocity c) I had no markable angular momentum. This was not for big intereset. Keep that in mind, maybe check for it. 6. In the "overset directory", modify your blockmesh according to the updated centre of mass and the controlDict such as starting time. 7. For my 6dof body I need the last position of the body. I do not found a way to get this via openfoam. So I had to use paraView instead. Therefore go to the latest time step. a) ExtractBlock - with the overset body. b) Mark ExtractBlock in the pipeline --> "File" --> "Save Data" --> "MyMovinBody.stl" c) Use this file in the new 'overset/constant/triSurface' folder d) Use the same name as before for the stl file or change snappyHexMesh & surfaceFeatureExtractDict to new name. 8) execute all commands related to mesh generation as before (blockMesh, snappy, mergeMesh , ...) -------------------------------------------------- 9) Only in case you refined or changed the oversetmesh: cp ./'time'/zoneID ./'time'/zoneID.orig -------------------------------------------------- 10) execute mapFields to mirror field values from the reconstructed folder to the created your_last_time_step folder: mapFields ../former_backgrounf_directory -sourceTime your_last_time_step -mapMethod cellPointInterpolate -noFunctionObjects -consistent 11) after mapping pointDisplacement file gets an extension to: pointDisplacement.unmapped remove this by: cp -R ./7/pointDisplacement.unmapped ./7/pointDisplacement -------------------------------------------------- 12) Only in case you refined or changed the oversetmesh. Get back the zoneIDs from the new mesh by: cp ./'time'/zoneID.orig ./'time'/zoneID -------------------------------------------------- 14) re-run Thanks again Diyanosh. This gave me a lot more understanding in how openFoam works. Best regards Michael |
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latest time, latesttime, mesh courant, overset, restart |
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